package com.sniper.springmvc.scheduler;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.Future;
import java.util.concurrent.RecursiveTask;

public class CountTask extends RecursiveTask<Integer> {

    private static final long serialVersionUID = 1L;
    private static final int THRESHOLD = 2;// 颜值
    private int start, end;

    public CountTask(int start, int end) {
        super();
        this.start = start;
        this.end = end;
    }

    @Override
    protected Integer compute() {

        int sum = 0;

        boolean canCompute = (end - start) <= THRESHOLD;
        if (canCompute) {
            for (int i = start; i <= end; i++) {
                sum += i;
            }
        } else {
            // 如果任务大于法制，就分裂成2个子任务 计算
            int middle = (start + end) / 2;
            CountTask leftTask = new CountTask(start, middle);
            CountTask rightTask = new CountTask(middle + 1, end);
            // 执行子任务
            leftTask.fork();
            rightTask.fork();
            // 等待任务执行完毕，并得到其结果
            int leftResult = leftTask.join();
            int rightResult = rightTask.join();
            // 合并子任务
            sum = leftResult + rightResult;
        }
        return sum;

    }

    public static void main(String[] args) {
        ForkJoinPool forkJoinPool = new ForkJoinPool();
        CountTask countTask = new CountTask(1, 4);
        Future<Integer> result = forkJoinPool.submit(countTask);

        try {
            // 是否有异常
            if (countTask.isCompletedAbnormally()) {
                System.out.println(countTask.getException());
            }
            System.out.println(result.get());
        } catch (InterruptedException | ExecutionException e) {
            e.printStackTrace();
        }
    }

}
